1. Field of the Invention
This invention relates generally to the field of magnetic recording heads (or write heads) having coils inducing magnetic flux for writing on a magnetic medium (such as a magnetic disc) and more particularly, to recording heads having coil sizes taller in height and turns of the coil being positioned close relative to each other, resulting from damascene manufacturing and chemical mechanical polishing (CMP) techniques, thereby causing stronger magnetic field, lower coil resistance, minimal write-induced protrusion and higher data rates.
2. Description of the Prior Art
Magnetic hard drives (or disc drives) have been in common use for storage of large groups of data for decades. Improvements in manufacturing thereof has attracted popular attention particularly to reducing the size of the drive and/or its internal components to achieve both lower costs and wider applications.
Magnetic hard drives include magnetic recording head for reading and writing of data. As well known, a magnetic recording head generally includes two portions, a write head portion or head for writing or programming magnetically-encoded information on a magnetic media or disc and a reader portion for reading or retrieving the stored information from the media.
Data is written onto a disc by a write head that includes a magnetic yoke having a coil passing there through. When current flows through the coil, a magnetic flux is induced in the yoke causing a magnetic field to fringe out at a write gap in a pole tip region. It is this magnetic field that writes data, in the form of magnetic transitions, onto the disk (or disc). Currently, such heads are thin film magnetic heads, constructed using material deposition techniques such as sputtering and electroplating, along with photolithographic techniques, and wet and dry etching techniques.
Examples of such thin film writers include a first magnetic pole, formed of a material such as NiFe which might be plated after sputter depositing an electrically conductive seed layer. Opposite the pole tip region, at a back end of the magnetic pole, a magnetic back gap can be formed. A back gap is the term generally used to describe a magnetic structure that magnetically connects first and second poles to form a completed magnetic yoke, as will be described.
One or more electrically conductive coils (or coil layers in photolithography techniques) can be formed over the first pole, between the pedestal and the back gap and can be electrically isolated from the pole and yoke by an insulation layer, which could be alumina (Al2O3) or hard baked photoresist.
With reference to FIG. 1, a plan view of an exemplary write element 302 can be seen in relation to the slider 111. A coil 304, passing through a magnetic yoke 306, induces a magnetic flux in the yoke 306. The magnetic flux in the yoke 306, in turn causes a magnetic field to fringe out at the pole tip 308. It is this fringing field 310 that writes magnetic signals onto a nearby magnetic medium.
With reference now to FIG. 2, a magnetic head 400 according to one possible embodiment of the present invention has magnetic read element 402 sandwiched between first and second magnetic shields, 404 and 406. A write head, generally referred to as 408, includes a first pole P1 410. A P1 pedestal 412 disposed in a pole tip region 413 and a first back gap layer 414, at an opposite end, are formed over the first pole. The first pole 410, P1 pedestal 412, and back gap 414 are formed of a magnetic material such as, for example NiFe. A first coil insulation layer 416 is formed over the first pole 410 between the P1 pedestal 412 and back gap layer 414. An electrically conductive coil 418, shown in partial cross section in FIG. 2, passes over the first pole 410 on top of the first insulation layer 416. A second coil insulation layer 420 insulates the turns of the coil 418 from one another and insulates the coil from the rest of the write head 408.
With continued reference to FIG. 2, a thin layer of non-magnetic write gap layer 424 is deposited over the coil 418, insulation layer 420 and P1 pedestal 412, and extends to an air bearing surface (ABS) 426 at one end and stops short of extending completely over the top of the back gap layer 414 at the other end. A magnetic second back gap material layer 428 may be formed over the top of the back gap layer 414, being magnetically connected therewith. The ABS is the surface of the magnetic head designed such that it enables the magnetic head to ride on a cushion of air between the head and the disc along the disc surface.
With continued reference to FIG. 2, a P2 pole tip 430 is provided on top of the write gap layer 424 in the pole tip region 413. The P2 pole tip 430 extends to the ABS 426, and has a width (into the page of FIG. 2) that defines a track width of the write head 408. The P2 pole tip is constructed of a magnetic material, and is preferably constructed of a soft magnetic material having a high magnetic saturation (high Bsat) and low coercivity.
With reference still to FIG. 2, a dielectric material such as alumina extends from the P2 pole tip 430 to the second back gap layer 428. The P2 pole tip 430 and the second back gap layer 428 may be formed at the same time or during the same step of processing, alternatively, they may be formed separately, as disclosed hereinabove. A second coil 434 sits atop the dielectric layer, and is insulated by an insulation layer 436, which could be for example hard baked photoresist. A P3 magnetic layer 438 is formed above the second coil 434 and the insulation layer 436 and extends from the P2 pole tip 430 to the second back gap layer 428 being magnetically connected with both. The P3 magnetic layer 438 forms the majority of a second pole of the magnetic yoke of the write head 408.
The pole tip region 426, the P3 magnetic layer 438 and the back gap 414 form the magnetic yoke (or yoke) referred to in the foregoing and below. It is desirable to maintain a short yoke length to keep the magnetic path short and thus to minimize magnetic leakage and to achieve high data rate for better performance. To do so, coil height need be increased and the coil turns placed closer together. Generally, more coil or copper results in stronger magnetic field and less resistance results in less heat generation, thus, less protrusion.
The problem with prior art write heads is that since it is desirable to keep the yoke length short, the coil (coils 418 and 434) needs to be narrow in an effort to attain an appropriate number of turns of the coil. The narrowness of the coil causes the coil resistance to be high. Therefore, the write head can become hotter during write operations thereby causing expansion and protrusion of the write head. This protrusion is likely to cause the write poles to protrude too close to the disc, potentially causing scratching of the disc.
Current damascene techniques allow for taller and closer coils. In damascene processes, trenches are formed in a first layer and a copper coil layer is formed over the trenches. Excess copper is then polished off leaving individual interconnect lines in the trenches. The removal of the excess copper is typically accomplished by chemical mechanical polishing (CMP). Although there are many known variations of the damascene method of metallization, the most common method for removing the excess copper is by CMP. CMP may also be used in removing other material during the manufacturing of coils. However, CMP generally results in overpolishing and corrosion, which is clearly undesirable in thin film heads. Therefore, the need arises for a write head of a disc drive to have a coil tall enough to have low resistance and closer turns, made with damascene and CMP techniques.